1. Field of the Invention
This invention relates to the automatic focusing operation of a camera, and more particularly to a device for determining the focusing position of the photographing lens.
2. Description of the Prior Art
In the case where, in order to perform macro-photography with an automatic focusing camera, the photographing lens is continuously focused on the object by extending it to a closest focusing distance of the order of 0.4 m beyond the range of ordinary photographing distances of from infinity to about 0.8 m, the photographing lens is displaced to the closest focusing distance from infinity. That is, the amount of movement of the photographing lens is large. Accordingly, a device for detecting the amount of movement of the photographing lens and a device for limiting the displacement of photographing lens are intricate, and the drive mechanism is also complicated. Furthermore, as it takes a relatively long time to displace the photographing lens, the time interval which elapses from the time instant that the shutter is released until the shutter is actually opened is also relatively long, which makes it difficult to perform the photographing operation.
Furthermore, a method of moving a close-up lens in front of the photographing operation with an automatic function auxiliarily used may be employed. However, in this case, the construction of the camera becomes intricate. Therefore, employment of the method is not practical.
On the other hand, there has been a demand for realization of the technique that, where it is required to take a picture of an object at a distance shorter than the close-up photographing distance limit, e.g., 0.8 m, in the range of ordinary photographing distances, the photographing lens can be focused on the object without using high photographing technique, i.e., by changing the close-up photographing distance limit directly (skipping over the intermediate distance) to a closest focusing distance of about 0.4 m for instance at the sacrifice of continuity.